Diaphragm for the reception and conversion of sound waves



April 6", 1926. 1,579,460

W. L. WALKER DIAPHRAGM FOR THE RECEPTION AND CONVERSION OF SOUND WAVES Filed Sep1', 20, 1922 I vwentoz Wizziam F WaMen 351 his Patented Apr. 6, 1926.

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WILLIAM L. WALKER, OF NEW YORK, N. Y., ASSIGNOR TO WALKER SIGNAL & EQUIP- MENT CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

DIAPHRAGM FOR THE RECEPTION AND CONVERSION OF SOUND WAVES.

Application filed September 20, 1922. Serial No. 589,344.

To all whom it may concern:

Be it known that I, IVILLIAM L. \VALKER, a citizen of the United States, residing in the borough of Manhattan, city, county, and State of New York, have invented certain new and useful Improvements in Diaphragms for the Reception and Conversion of Sound lVaves, of which the following is a full, clear, concise, and exact description.

This invention relates to vibrating diaphragms or plates for use in general where it is desired to transmit vibratory sound waves or convert the same into vibratory electric currents through the medium of microphones or similar devices. My invention is particularly applicable to submarine signalling systems where the special requirements and conditions are very exacting and has for its object the transmission or conversion of sounds with more faithfulness, accuracy, and efliciency than has heretofore been possible, and also to prevent corrosion of the diaphragm due to the action of sea water.

To obtain the best results in submarine sound detection when used on shipboard for signalling, navigational or other purposes, I have found that it requires the use of a comparatively thin diaphragm in the outer skin or plating of a vessel, the diaphragm being flush with the outer skin or surface and in direct contact with the water. A flush diaphragm reduces water noises to a considerable extentby making a fair stream line. Salt water however, will rapidly corrode the metal plates of which diaphragms are usually made and, furthermore. if the plates are made of a metal ordinarily noncorrodible, galvanic action will be set up when two dissimilar metals are in contact with each other and with salt water, and a still more rapid corrosion will take place. In either case the thin metal diaphragms will become useless in a comparatively short time and require replacing. This is objectionable from a practical standpoint as it involves eX pense and extra work.

Even if the so called rustless steels are used to prevent corrosion, I have found that they deteriorate and require replacement. Furthermore, these steels do not transmit vibrations so well as other metals or materials. I have found that a certain form of hard rubber, celastoid and similar insulating materials are best adapted'to overcome the above mentioned difficulties and when diaphragms made of these materials are used with other parts to give ample strength to Withstand unusual water pressures and Wave forces to which they are subjected, they are also very resilient so that they efficiently transmit weak vibrations and will last indefinitely.

In the reception of sounds in submarine signalling systems much difliculty has heretofore been experienced, in receiving the desired sounds and differentiating them from extraneous noises, such as those caused by the flow of water along the sides of a ship and those caused by movements on shipboard like the throb of the engines, pumps, steering apparatus, propellers and the like. One object, therefore, of my invention is to produce such an arrangement of parts as will reduce to a minimum all undesirable noises to reproduce true tones, to increase the reception of the desired transmitted sounds and to generally improve and intensify the action of sonant diaphragms.

For a detailed description of various forms of my improved diaphragm reference may be had to the following specification and to the accompanying drawing forming a part thereof, in which Figure 1 is a diametral sectional view of -a sound receiving device applied to the side of a ship or similar enclosure: Figure 2 is a plan view of a resilient cushion applied to the diaphragm of my improved device; Figure 3 is a modification thereof; Figure 4 is a diametral sectional view of a diaphragm having the cushioning means of Figure 3 applied thereto, and Figure 5 is a diametral sectional view of another modified form.

In the drawing the numeral 1 indicates the skin orv side of a ship or the wall of some similar enclosure and 2 indicates a sea chest, casing or protecting housing in which the sound receiving diaphragm and microphone are contained. The numeral 3 indicates the resilient diaphragm which is preferably made integral with a flanged supporting ring 4. The housing 2 is of comparatively large mass or weight and absorbs or damps lateral vibrations to a considerable extent. The diaphragm 3 is comparatively very light and will be easily set into motion by external weak vibrations. Owing to this construction the diaphragm is not readily affected by lateral vibrations but is very sensitive to transverse vibrations. By varying its size, thickness etc., this diaphragm may be damped by similar means, that is by varying the size and position of some of its I members. This diaphragm may be molded,

built up or cut from suitable material but preferably moulded, cut or otherwise formed from elastic, non-metallic, non-corrodible, insulating material.

Heretofore such diaphragms have been made of steel iron or non-corrodible metal but no metal has been found which will effectively resist salt water or galvanic action.

I have found that a special compound of hard rubber, celastoid (made from cellulose acetate) or a combination of bakelite with celastoid or similar materials are tough, have good elasticity and strength, are not affected by salt water or galvanic action and are therefore particularly suitable for this purpose. I believe that I am the first to use the compounds of this nature for diaphragms on ships and Ihave found them to be particularly adapted for the reception of submarine sounds and signals. The

flanged supporting ring 4 is interiorly 's'crew.

threaded to receive a screw threaded clamping ring or nut 5, adapted to hold the microphone supporting diaphragm 6, in position. This latter diaphragm is made of flat or if preferred corrugated steel or other thin resilient, metal or. material such as mica. The diaphragm 6 is of less diameter than the diameter of the diaphragm 3 or of the gaskets 10 and 11 so that its periphery does not come in contact with the inner surface of the ring or frame 4, it being supported in the desired position by said gaskets and the pressure of the ring 5 upon the gaskets 11 and 12 which pressure may be varied by adjusting the ring 5. The diaphragm 6 is therefore not affected so much by lateral as by transverse vibrations and these characteristics may be varied 'by varying the size of this diated if found desirable.

phragm. The diaphragm 6 is provided with a central boss or other attaching means 7 to which the threaded rod 8 of the microphone 9 is attached.

Between theouter diaphragm 3 and the inner diaphragm 6 there maybe placed a gasket 10 Figure 2, or a gasket 10 Figure Either one or the other of these parts may be omit- This pad and gaskets form cushioning means and are preferably made of soft rubber or similar resilient material. If a gasket and central acteristics may be given the diaphragm.-

Threaded ring or nut 5 not only gives an ad ustable pressure on' the outer and inner diaphragms but binds them and the gaskets J together thereby producing great resistance and strength to withstand external pressure and forces without impairing the sensitiveness of the diaphragm. The gaskets 10 and 11 and the disk 13 are of such dimensions that they constitute resilient cushions which transmit vibrations of certain periods but cause the diaphragms to be aperiodic to other vibrations. In other words said parts serve as a filter for undesirable sounds, especially ship noises, which are not harmonic in wave form, such as crackling, rushing, knocking or hissing sounds.

In thevmodification illustrated in Figures 3 and 4 the radial-supporting spokes are omitted and the central soft rubber disk .13 is centered on the outer diaphragm 3 by means of a central boss 14 which enters a hole 15 in the disk 13. Other means of locating said disk will be apparent to those skilled in the art, but I have found it preferable not to have said disk cemented or otherwise directly attached to either diaphragm.

In Figure 5 a modified form of diaphragm "'is illustrated being one in which the microphone is attached directly to the outer plate.

The construction there shown is particularly adapted for use with containers or housings where it is desirable to insert or remove the diaphragm from the outside, instead of from the inside, as provided by the construction of Figure 1. Such containers are those where tanks are used on the in-,

side of the hull without openings through the skin of the vessel as illustrated in my applicatibn Serial No. 552,023, filed April 12, 1922, in which the microphones and container are suspended in a tank which is in contact with the side of the ship.

In this form of the invention the numeral 20 is a portion of the wall ofa container or housing such as above referred to. The ring or frame 21 is screw threaded both interiorly and exteriorly and is adapted to be retained in a flanged opening in the wall of said container. The ring or frame 21 is preferably made integral with, and supports the diaphragm 22, which is provided with a central boss or other means 23 for engaging the threaded rod 24, of the microphone 25. An adjustable clamping ring 26 engages the interior threads of the ring 21 and produces a variable pressure on a gasket'27, of soft rubber or similar material inserted between the margin of the diaphragm 22 and said ring. A gasket or packing 28 of suitable material is inserted between the ring or frame 21 and an internal flange in order to make the parts water tight and prevent leakage.

The adjustment of the pressure of the ring 26 on the gasket 27 and consequently on the diaphragm 22, serves to make the latter more resonant to desired sounds and reduces extraneous noises. This effect may also be further brought about by varying the sizes of the parts, such as the thickness and diameter of the gasket 27 and those of the diaphragm 22.

Having thus described these forms of my invention, 1 do not wish to be understood as being limited to the details of form and arrangements of parts illustrated herein, for various changes may be made by those skilled in the art without departing from the spirit and scope of my invention.

lVhat I claim and desire to protect by Letters Patent is:

1. A sonant diaphragm adapted to be inserted in an opening in and forming a continuous portion of the skin of a ship comprising a resilient plate of hard, dense, noncorrodible, insulating material of sufiicient size and thickness to resist water pressure and be responsive to vibrations of transmitted signals, means for supporting the margin of said plate in position, and sound transmitting means adapted to be operated by said plate.

2. A sonant diaphragm adapted to be in serted in an opening in and forming a continuous portion of the skin of a ship comprising a resilient plate of hard, dense, noncorrodible, insulating material of suflicient size and thickness to resist water pressure and be responsive to vibrations of transmit ted signals, a supporting frame of said material integrally connected therewith, and sound transmitting means adapted to be operated by said plate.

3. A sonant diaphragm adapted to be inserted in an opening in and forming a continuous portion of the skin of a ship comprising a resilient plate of hard, dense, vulcanized rubber of sufficient size and thickness to resist water pressure and be responsive to vibrations of transmitted signals, a supporting frame or ring of said material integrally connected therewith, and sound transmitting means adapted to be operated by said plate.

4. A sonant receiving and transmitting device adapted to be inserted in an opening in and forming a continuous portion of the skin of a ship comprising a plurality of resilient diaphragms, the outer diaphragm being of suflicient size and thickness to resist water pressure and be responsive to vibrations of transmitted signals, a resilient cushion between said diaphragms, arid sound transmitting means connected with one of said diaphragms.

5. A sonant receiving and transmitting device adapted to be inserted in an opening in and forming a continuous portion of the skin of a ship comprising two resilient dianhragms, the outer diaphragm being of sufficient size and thickness to resist water pressure and be responsive to vibrations of transmitted signals, a resilient soft rubber cushion between said diaphragms, and sound transmitting means connected with one of said diaphragms.

6. A sonant receiving and transmitting device comprising two resilient diaphragms, a resilient pad between the central portions of said diaphragms, and sound transmitting means connected with one of said diaphragms.

7. A sonant receiving and transmitting device comprising two resilient diaphragms, a resilient pad of soft rubber between said diaphragms, and sound transmitting means connected with one of said diaphragms.

8. A sonant receiving and transmitting device comprising two resilient diaphragms, a resilient pad of soft rubber between said diaphragms, a resilient gasket between the margins of said diaphragms, and sound transmitting means connected with one of said diaphragms.

9. A sonant receiving and transmitting device comprising two resilient diaphragms, a resilient pad of soft rubber between said diaphragms, a resilient gasket between the margins of said diaphragms, a resilient gasket in contact with one of said diaphragms, means for producing a variable pressure on said gaskets and diaphragms, and sound transmitting means connected with one of said diaphragms.

10. A sonant receiving and transmitting device comprising two resilient diaphragms, resilient cushioning means between said diaphragms, a resilient gasket bearing on the opposite side of one of said diaphragms, a ring adapted to produce a variable pressure on the last named gasket, and sound transmitting means connected with one of said diaphragms.

11. A sonant receiving and transmitting device comprising a diaphragm of hardresilient material, a supporting ring integrally connected therewith, a second diaphragm within but not touching said ring, a soft resilient pad between said diaphragms, a resilientgasket between the margins of said diaphragms, a resilient gasket bearing on the inner side of one of said diaphragms, a

threaded ring within said supporting ring a and adapted to produce a variable pressure on the last named gasket, and sound transmitting means connected with one of said diaphragms.

12. A sonant receiving and transmitting device comprising a diaphragm of hard rubthreaded ring within said supporting ring her or similar material, a supporting ring and adapted to produce a variable pressure 10 integrally connected therewith, a second diaon the last named gasket, and sound transphragm of resilient material within said mitting means connected with one of said ring, a soft resilient pad between said diadiaphragms.

phragms, a gasket between the margins 015 Signed this 13th day of September 1922.

said diaphragms, a gasket bearing on the inner side of the last named diaphragm, a VILLIAM L. WALKER. 

